In a turbine engine, the turbine section includes a rotor. A plurality of discs are provided on the rotor; the discs are axially spaced from each other. A plurality of blades are mounted on each disc to form a row of blades. The blades are arrayed about the periphery of the disc and extend fan outward therefrom.
Along the axial direction of the turbine, rows of blades alternate with rows of stationary airfoils or vanes. Unlike the blades, the vanes are attached at a radially outer end to a turbine casing and extend radially inward therefrom to a radially inner end. Because the rows of stationary airfoils and the rows of rotating airfoils are spaced from each other, there are axial gaps between these components.
Hot gases from the combustor section of the engine are directed to the turbine section where they engage the vanes and blades, causing rotation of the blade fans and the rotor. The blades and vanes are designed to withstand the high temperature of the combustion gases. In contrast, the radially inner components, such as the discs, can fail if exposed to the hot combustion gases. Accordingly, these components must be protected from the hot combustion gases.
The discs can be shielded from the hot gases by seal plates that are secured to the discs. The major function of the rotor seal plates in the turbine section is to separate the hot gas path from the blade carrying structure, i.e. from the disks. Among many other design requirements, the seal plates also lock the blades into position axially. This axial locking of a turbine blade is typically realized by seal plates on both the forward, intake side and the aft, exhaust side. Each of these seal plates axially locks the blade to one direction. This functional split prevents turbine blades from being disassembled in an enclosed engine because the intake seal plate cannot be accessed unless the turbine casing is lifted. As a consequence, the turbine casing cover needs to be disassembled if a stage 4 blade exchange becomes necessary, creating tremendous work and time effort, potentially leading to increased outage times.